Current retractor systems for lateral spine surgical procedures create a round opening through the psoas muscle, which includes muscle fibers running mostly in the cranial-caudal direction. These systems sequentially inserted round dilators which dilate the surgical site radially away the initial dilator/K-wire insertion point, which can lead to compression of nerves and blood supply on the transverse process of the vertebral body. Existing retractor systems include the ability to monitor the most posterior point of each instrument being entered into the psoas, but continue to introduce larger instruments into the area of concern. These previous systems also typically include two, three or four round dilators that must first be forced into the muscle tissue before the retractor can be inserted around the largest dilator. These round dilators, coupled with multi-blade retractors that spread radially, can cause muscular trauma, and can further stretch or compress nerve roots in the surrounding tissue.